The invention relates to antibiotic compositions including a tetracycline-type compound. The term "tetracycline-type" compound refers to tetracycline, chlortetracycline, doxycycline and particularly oxytetracycline or their pharmacologically acceptable salts, especially the dihydrate salt of oxytetracycline.
It is known in the art to use 2 pyrollidone as a co-solvent in the preparation of an aqueous solution containing more than 20% by weight of oxytetracycline. The intramuscular injection of such solutions however is relatively painful and may be accompanied by a necrotic reaction at the site of injection.